JPH0742560B2 - High temperature spring manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high temperature spring that is used for a long time at high temperature in various machines and devices.

(Prior Art) High-temperature springs are used in various machines and devices such as steam turbines, gas turbines, and other internal combustion engines that are used at high temperatures for a long time.

The high temperature springs used in the past are 0.1% carbon by weight%
Below, silicon 1% or less, manganese 1% or less, chromium 10-20
%, Aluminum 0.3-1%, titanium 2-3%, niobium
It is formed into a predetermined spring shape such as a wire rod, rod, plate, etc. of a Ni-based precipitation strengthening alloy consisting of 0.5 to 1.5%, iron 5 to 10% and the balance nickel, and then aged.

However, when this conventional spring is used at a high temperature, the spring strength sharply decreases due to relaxation due to the passage of time, and it is not possible to always maintain a constant spring strength. There is a drawback that the spring strength cannot be maintained for a long time within the design value range. Further, there is a drawback that the spring strength is small with respect to the temperature rise and miniaturization of various machines and equipment due to the recent improvement in thermal efficiency.

(Problems to be Solved by the Invention) The present invention has been made in view of such conventional circumstances.
The purpose of the present invention is to provide a method for manufacturing a high-temperature spring that has a stronger spring strength than conventional high-temperature springs and that is less likely to be deformed or relaxed due to relaxation during use and has excellent strength-relaxation resistance. is there.

(Means and Actions for Solving the Problems) The present invention is a solution of a Ni-based precipitation strengthening alloy wire material, a bar material, or a plate material, which is a spring material, at 980 ° C. or higher, and a majority of its metallographic structure is equiaxed. And the step of forming the spring strength into a shape that exceeds the required strength, and the stable spring strength with little change in spring strength during use due to stress load heating during use of the high temperature spring. The method for manufacturing a high temperature spring is characterized in that the high temperature spring is manufactured through a stabilization treatment process for imparting strength.

In addition, the spring material is less than 0.1% carbon by weight,
Silicon 1% or less, Manganese 1% or less, Chromium 10-25%, Aluminum 0.1-1%, Titanium 0.1-2%, Niobium 1.5-
A method for manufacturing a high temperature spring, which is an alloy composed of 6%, iron 2 to 25%, molybdenum 2 to 10%, and balance nickel, and is formed through the above-mentioned steps.

Here, the reason for limiting each step of the present invention will be described.

First of all, the reason for the process of solution-treating a wire rod, rod or plate of Ni-based precipitation strengthening alloy, which is a spring material, at 980 ° C or higher, and making the majority of its metallographic structure equiaxed is hot forging, hot rolling This is because when most of the working processes such as rolling or hot drawing are not performed, relaxation resistance cannot be obtained. The solution treatment temperature is preferably 980 ° C. or higher, and more preferably 1000 ° C. or higher in order to achieve the solution treatment effect and to make the majority of the metal structure into equiaxed crystals.

Also, some cold working may be added after the solution treatment.

Next, the reason for the step of forming the spring strength into a shape that is equal to or greater than the required strength is that it is necessary to obtain the required spring strength and shape by the stabilization process in the next step. This is because, if the desired shape is set from the beginning, the predetermined spring strength and shape cannot be obtained by the deformation due to the stabilization process.

Next, the reason for the stabilization process is to provide stable spring strength with little change in spring strength during use due to stress load heating during use of the high-temperature spring. This is for imparting the zation property.
Without this stabilization process, the spring strength and spring shape change greatly during use at high temperatures, and a high temperature spring that exhibits stable spring strength for a long time cannot be obtained.

In this stabilization process, after setting the spring strength to the required strength or higher, the spring strength of the high-temperature spring is set to the allowable range of the predetermined width set at the design stage by heating the high-temperature spring under stress load. By lowering the design value to the designed value by relaxation, a stable spring strength with a small change in spring strength can be obtained. This means that the stress applied at this time does not need to be applied with the same stress as that during use.

Here, the stress-loading heat when the high-temperature spring is in use means that the high-temperature spring is used in a state in which various stresses such as compression, tension or bending are applied depending on its application. The heating is performed under the same compression, tension or bending as the stress condition. The heating conditions and stress can be set appropriately depending on the heating temperature, time, and the like.

The stabilizing process is preferably performed after the aging treatment, but may also be performed as the aging treatment.

Next, the reason for limiting the composition of the Ni-based precipitation strengthening alloy that is a spring material is that it can be processed into a wire rod, a rod material or a plate material, and that it can be easily formed into a required spring shape, which is superior to conventional high temperature springs. This is due to the fact that relaxation resistance is obtained.

The reasons for limiting the composition of the preferable Ni-based precipitation strengthened alloy will be described below.

Carbon (C) is an element necessary for forming a solid solution in the alloy and improving the strength. However, when a large amount is contained, carbide precipitates at the grain boundaries and impairs intergranular corrosion resistance and toughness. Therefore, the carbon content is preferably 0.1% by weight or less. More preferably, it is about 0.02 to 0.06% by weight.

Silicon (Si) is an element added as a deoxidizing agent during dissolution. However, since a large content impairs toughness and workability,
The content of silicon is preferably 1% by weight or less. More preferably, it is about 0.1 to 0.6% by weight.

Manganese (Mn) is an element added as a deoxidizing and desulfurizing agent during dissolution. However, even if added in a large amount, the effect becomes small, so that the manganese content is preferably 0.1% by weight or less. More preferably, it is about 0.1 to 0.5% by weight.

Chromium (Cr) is an element necessary for improving the strength, oxidation resistance and corrosion resistance of the alloy. However, if the amount is too small, the effect is small, and conversely, if the amount is too large, the workability is impaired, so the content of chromium is 10 to 25% by weight.
Is preferred. It is more preferably 15 to 20% by weight.

Aluminum (Al) is an element necessary for improving the strength of the alloy by forming an intermetallic compound with nickel and depositing it in the alloy. However, if the amount is too small, the effect is small. On the other hand, if the amount is too large, the content of titanium or niobium may be compromised, but the workability is impaired. Therefore, the aluminum content is preferably 0.1 to 1% by weight. . More preferably, it is 0.2 to 0.7% by weight.

Titanium (Ti) is an element necessary to improve the strength of the alloy by forming an intermetallic compound with nickel, similar to aluminum. However, if the amount is too small, the effect is small, and conversely, if the amount is too large, the workability is impaired though there is a balance of the contents of aluminum and niobium.
The titanium content is preferably 0.1 to 2% by weight. More preferably, it is 0.2 to 2% by weight.

Niobium (Nb) is an element necessary for improving the wear resistance and strength of the alloy by forming an intermetallic compound with nickel like aluminum and titanium. However, if the amount is too small, the effect is small. On the contrary, if the amount is too large, the content of aluminum and titanium may be compromised, but the workability is impaired. Therefore, the content of niobium is 1.5 to 6% by weight.
Is preferred.

Iron (Fe) is an element necessary for improving the hot workability of the alloy. However, if the amount is too small, the effect is small, and if the amount is too large, the corrosion resistance is impaired.
The iron content is preferably 2 to 25% by weight.

Molybdenum (Mo) is an element required to improve the strength of the alloy and the corrosion resistance. However, if the amount is too small, the effect is small, and conversely, if the amount is too large, the workability is impaired. Therefore, the content of molybdenum is preferably 2 to 10% by weight. (Example) Example 1 Using a high frequency induction melting furnace, C: 0.31% in weight% and Si: 0.23
%, Mn: 0.2%, Cr: 18.4%, Fe: 17.5%, Ti: 0.77%, Al: 0.43
%, Nb: 5.4%, Mo: 3.6%, the balance Ni was obtained.

Next, hot forging and wire drawing are applied to this ingot,
The wire rod has a diameter of 1.4 mm.

A part of the wire rod thus obtained was cut out, heated at 1020 ° C. for 30 minutes and then rapidly cooled, and then cold drawn to obtain a wire rod having a diameter of 1.2 mm.

Continued, this wire rod has a center diameter of 11 mm, a free length of 21.5 mm, and an effective number of turns.
After forming a coil spring 4.5 times and 6.5 times in total, 718 ℃
The spring strength was made equal to or higher than the required strength by performing an aging treatment for 8 hours at 621 ° C. for 8 hours.

Further, this coil spring was compressed and subjected to a stabilization treatment at 700 ° C. for 25 hours in a state where the coil length was 12 mm, and the test was performed. As a result of observing the metal structure of the coil spring, it was an equiaxed crystal in which twins were seen.

Comparative Example 1 The wire rod having a diameter of 1.2 mm used in the above Example 1 has a center diameter of 11 mm,
After forming a coil spring with a free length of 20 mm, an effective number of turns of 4.5, and a total number of turns of 6.5, aging treatment was performed at 718 ° C for 8 hours and 621 ° C for 8 hours to make the spring strength more than the required strength. That is, the coil spring of Example 1 was used for the test without the stabilization treatment.

Comparative Example 2 A wire having a diameter of 1.2 mm was cut by cutting out a part of the wire having a straightness of 1.4 mm used in Example 1 above, heating at 954 ° C. for 1 hour and then rapidly cooling.

Next, this wire rod has a center diameter of 11 mm, a free length of 21.5 mm, and an effective number of turns.
After forming a coil spring 4.5 times and 6.5 times in total, 718 ℃
8 hours and 621 ° C. for 8 hours.

Further, this coil spring was compressed and subjected to a stabilization treatment at 600 ° C. for 15 hours in a state where the coil length was 12 mm, and the test was performed.

Comparative Example 3 C: 0.06%, Si: 0.13 by weight% which is a conventional high temperature spring material.
%, Mn: 0.62%, Cr: 15.4%, Fe: 7.2%, Ti: 2.5%, Al: 0.83
%, Nb: 0.82%, balance Ni was melted in a high frequency induction melting furnace to obtain an alloy ingot.

Next, hot forging and wire drawing are applied to this ingot,
Made of wire with a diameter of 1.4 mm.

A part of the wire rod thus obtained was cut out, heated at 1093 ° C. for 30 minutes and then rapidly cooled, and then drawn cold to obtain a wire rod having a straight line of 1.2 mm.

Continued, this wire rod has a center diameter of 11 mm, a free length of 20 mm, and an effective number of turns 4.
After forming the coil spring 5 times and the total number of turns 6.5 times, the coil spring was subjected to an aging treatment at 650 ° C. for 5 hours and subjected to the test.

In the test, the compression coil springs of Example 1 and Comparative Examples 1 to 3 described above were loaded into a furnace at 600 ° C. and 700 ° C. in a state of being compressed and fixed to 12 mm, heated for a predetermined time, taken out to room temperature, and the weight was removed. After that, the free length of the spring and the load required to compress the spring length to 12 mm were measured. The test results are shown in FIGS. 1 and 2. The metal structure of the spring was equiaxed.

As is clear from FIG. 1 and FIG. 2, the high-temperature spring according to the present invention, which has high strength and excellent relaxation resistance, is in a state in which stress is applied at high temperature for a long time as compared with the spring of the comparative example. Even when used, the coil length and spring strength have hardly changed. More specifically, the embodiment 1 according to the present invention, in which the spring strength equal to or higher than the required strength of the present invention is applied and then subjected to the stabilization process, is the spring strength having an allowable range of a predetermined width at the design stage. Comparative Example 1 which has a stable spring strength for a long time within the range of the design value of 1. Has a sharp decrease in its spring strength. In this way, if the spring strength is used in a state where high spring strength is imparted without performing the stabilization process, the spring strength sharply decreases at the time of use. After applying the spring strength, it is not possible to obtain a stable spring strength for a long time unless the spring strength is reduced to within the design value range by the stabilization process.

Further, in the present invention, when the spring strength to be reduced by the stabilization process, in other words, the spring strength within the range of the design value is obtained from the beginning, the spring strength is reduced as in Comparative Example 2 or Comparative Example 3. Only, there is no way to get stable spring strength for a long time.

As described above, the high temperature spring produced by the method for producing a high temperature spring according to the present invention has excellent relaxation resistance and is an industrially useful spring that can always maintain a constant spring strength for a long time. I understand.

(Effects of the Invention) The method for manufacturing a high temperature spring of the present invention has a strength higher than that of the conventional high temperature spring, and is less likely to be deformed by relaxation during use and to be reduced in spring strength. An excellent high temperature spring can be obtained.

[Brief description of drawings]

FIG. 1 and FIG. 2 show that the high-temperature spring according to the present invention having excellent strength and relaxation resistance and the high-temperature spring of the comparative example were loaded with a load and heated to a spring length of 12 mm, and then heated. FIG. 7 is a characteristic diagram showing the test results of measuring the free length of the spring when removing the and the load required to compress the spring length to 12 mm.

Claims (2)

[Claims] 1. A wire rod of Ni-based precipitation strengthening alloy, which is a spring material,
A process in which a bar or plate is subjected to solution treatment at 980 ° C or higher to make the majority of the metallographic structure equiaxed, a process in which the spring strength exceeds the required strength, and a high temperature spring. The method for producing a high-temperature spring, characterized in that the high-temperature spring is produced through a stabilization treatment step of providing a stable spring strength with a small change in spring strength during use due to stress load heating in use. 2. The spring material is 0.1% carbon by weight.
Below, silicon 1% or less, manganese 1% or less, chromium 10-25
%, Aluminum 0.1 to 1%, titanium 0.1 to 2%, niobium
The method of manufacturing a high temperature spring according to claim 1, wherein the alloy is an alloy composed of 1.5 to 6%, iron 2 to 25%, molybdenum 2 to 10%, and the balance nickel.